Temperature control in the manufacturing of Dyes and Pigments29 July 2015
Dyes and Pigments are widely used in the plastic, coating, textile and other industries to impart colour. In the production process, things can get pretty heated !... literally.
An exothermic chemical reaction takes place in the reactors where the colourful products are synthetized. For quality and safety reasons, a strict control of the temperature during the synthesis process is key to avoid unwanted and sometimes dangerous chemical reactions. Indeed, the exposure of the dyes and pigments to heat can easily alter their colour and quality. Moreover, the pressure build-up during the diazotation reaction, with heat can raise some critical safety issues.
Advanced industrial refrigeration and the latest development in flake-ice technology now enable to service this need and to manage accurate temperature control of the batching process. The systems has been successfully tested by leading pigment manufacturers in Germany and in India.
Each pigment has a different reaction to higher temperature, according to its chemical properties and material.
Too hot temperature (or a too long exposure to high temperature), may completely degrade the product colour and quality. Certain colours are more susceptible to this drift, depending on the application. Heat may also cause dangerous chemical reactions. Each production process being different, the temperature control must be quick and accurate.
Flake-ice quickly cools the mix
For this application, flake ice is the most appropriate cooling medium. It is pure cooling energy which can be disbursed as of need, by mixing it with the other ingredients. It has a large heat-exchange surface- area and consequently provides effective and very fast cooling of the product mix in the vats. There is no water mixed with the flake ice. The "ice only" feature of the flake-ice manufacture, means that the latent heat of fusion of the ice, the principal source of the cooling energy, is 100 % available for cooling the mix. The response in temperature drop to the introduction of flake ice into the reactors is almost immediate. Hence the accuracy of the temperature control and colour. One kg of ice precisely draws 334 kJ of heat from the mix.
Furthermore, the consistency of the dry flake-ice enables precise calculations to be made of its cooling input by production managers in the dye and pigment industries.
The German manufacturer KTI-Plersch has installed automated flake-ice production and dosing systems for most of the industry leaders throughout the world.